Unit 5

• Four Main Components of Blood

  • Red Blood Cells
  • Platelets
  • Plasma
  • White Blood Cells
• Plasma


  The liquid bit of blood, which is blood minus the blood cells
• What Plasma Carries


  • Red and white blood cells and platelets
  • Digested food products (like glucose and amino acids) from the gut to all the body cells
  • Carbon dioxide from the body cells to the lungs
  • Urea from the liver to the kidneys (where it's removed in the urine)
  • Hormones, which act as chemical messengers
  • Heat energy
• Pathogens


  Microorganisms that cause disease, e.g. certain types of bacteria and viruses
• Types of White Blood Cells

  • Phagocytes
  • Lymphocytes
• Phagocytes


  • Detect things that are 'foreign' to the body, e.g. pathogens, then engulf and digest them
  • Non-specific - they attack anything that's not meant to be there
• Platelets


  • Small fragments of cells that help blood clot
  • When you damage a blood vessel, platelets clump together to 'plug' the damaged area
  • In a clot, platelets are held together by a mesh of a protein called fibrin
• Red Blood Cells


  • Small and have a biconcave shape to give a large surface area for absorbing and releasing oxygen
  • Contain haemoglobin, which reacts with oxygen to become oxyhaemoglobin in the lungs, and the reverse reaction happens to release oxygen to the cells
  • Don't have a nucleus - this frees up space for more haemoglobin, so they can carry more oxygen
• Lymphocytes


  Produce proteins called antibodies that lock on to invading pathogens and mark them out for destruction by other white blood cells
• Antibody Production


  1. Lymphocytes come across a foreign antigen

  2. Lymphocytes start to produce antibodies specific to that antigen

  3. Antibodies flow round the body to mark all similar pathogens

  4. Memory cells are also produced that can quickly reproduce antibodies if the same antigen enters the body again
• Vaccination


  Involves injecting dead or inactive pathogens into the body to trigger an immune response and produce antibodies, without causing illness
• Types of Blood Vessels

  • Arteries - carry blood away from the heart
  • Capillaries - involved in the exchange of materials at the tissues
  • Veins - carry blood to the heart
• Arteries


  • Carry blood under high pressure, so have strong and elastic walls
  • Contain thick layers of muscle to make them strong
  • The largest artery is the aorta
• Capillaries


  • Really tiny, carrying blood close to every cell in the body
  • Have permeable walls to allow diffusion of substances in and out
  • Supply food and oxygen, and take away wastes like CO2
  • Walls are usually only one cell thick to increase the rate of diffusion
• Veins


  • Carry blood at lower pressure, so don't need as thick walls as arteries
  • Have a bigger lumen than arteries to help the blood flow
  • Have valves to help keep the blood flowing in the right direction
  • The largest vein is the vena cava
• Exercise increases heart rate

  • Exercise increases the amount of carbon dioxide in the blood
  • High levels of blood CO2 are detected by receptors in the aorta and carotid artery
  • These receptors send signals to the brain
  • The brain sends signals to the heart to increase the heart rate
• Arteries carry blood away from the heart, and veins carry blood back to the heart
• pulmonary


  To do with the lungs
• Learning the names of the blood vessels in this diagram will be a lot easier if you can remember what these three words mean
• hepatic


  To do with the liver
• renal


  To do with the kidneys
• When you exercise, your muscles need more energy, so you respire more
• You need to get more oxygen into the cells and remove more carbon dioxide
• For this to happen the blood has to flow faster, so your heart rate increases
• Exercise increases the amount of carbon dioxide in the blood


  1. High levels of blood CO2 are detected by receptors in the aorta and carotid artery

  2. These receptors send signals to the brain

  3. The brain sends signals to the heart, causing it to contract more frequently and with more force
• Hormonal System Also Helps to Control Heart Rate
• When an organism is threatened (e.g. by a predator) the adrenal glands release adrenaline


  1. Adrenaline binds to specific receptors in the heart

  2. This causes the cardiac muscle to contract more frequently and with more force, so heart rate increases and the heart pumps more blood

  3. This increases oxygen supply to the tissues getting the body ready for action
• You need to know the heart in a fair bit of detail
• Sketch out the heart diagram and see if you can put all the labels on. Keep trying till you can
• coronary


  Relating to the heart
• Coronary heart disease is when the coronary arteries that supply the blood to the muscle of the heart get blocked by layers of fatty material building up
• This causes the arteries to become narrow, so blood flow is restricted and there's a lack of oxygen to the heart muscle- this can lead to a heart attack
• There are many risk factors for coronary heart disease. Risk factors are things that are linked to an increase in the likelihood that a person will develop a certain disease during their lifetime
• One risk factor for coronary heart disease is having a diet high in saturated fat. This can lead to fatty deposits forming inside arteries, which can lead to coronary heart disease
• Smoking is another risk factor for coronary heart disease. Smoking increases blood pressure which can cause damage to the inside of the coronary arteries. Chemicals in cigarette smoke can also cause damage. The damage makes it more likely that fatty deposits will form, narrowing the coronary arteries
• Another risk factor for coronary heart disease is being inactive. It can lead to high blood pressure. which can damage the lining of arteries. This damage makes it more likely that fatty deposits will form
• Excretion


  The removal of waste products
• Kidneys


  Excretion organs
• The kidneys are part of the urinary system
• The kidneys perform three main roles

  • Removal of urea from the blood
  • Adjustment of ion (salt) levels in the blood
  • Adjustment of water content of the blood